1. Field of the Invention
One disclosed aspect of the embodiments relates to an image forming apparatus which employs an electrophotographic process.
2. Description of the Related Art
A tandem type image forming apparatus which employs an electrophotographic process is known. In the tandem type image forming apparatus, image forming units are provided to independently form toner images in respective colors, and the formed color toner images are sequentially transferred to be superimposed on one another to form a color image. In the tandem type image forming apparatus, an optical magnification in a main scanning direction (hereinafter, main scanning magnification) may differ among the respective colors, so that color misregistration may occur.
Japanese Patent Application Laid-Open No. 2001-5245 discusses a method for correcting such variations in the main scanning magnification by inserting or deleting into or from image data a pixel or a resolved pixel having a resolution equal to or higher than the resolution of the image data (hereinafter, referred to as a “pixel piece”). More specifically, if the main scanning magnification is less than an appropriate value (i.e., if the width in the main scanning direction is reduced), a pixel or a pixel piece is inserted according to the reduction rate. Meanwhile, if the main scanning magnification is greater than the appropriate value (i.e., if the width in the main scanning direction is expanded), a pixel or a pixel piece is deleted according to the expansion rate.
In such a method for correcting the main scanning magnification by inserting or deleting a pixel or a pixel piece, however, interference may occur between the pattern of positions into or from which the pixel or the pixel piece is inserted or extracted and the screen pattern or the image data pattern, which in turn may result in moire.